Bought the Necro DLC during the recent sale and started a seasonal Necro, now completed the free 6pc set and farming materials/legendaries at Torment 7 to round out my build (Trag'oul Blood Mages).

In non-seasonal, the same monk which hit a wall at GR79 in Season 6 is now capable of GR95 or higher (with enough paragon) thanks to major buffs in patch 2.6.1. All class builds probably can solo GR90++ now easily, which is insane.

I think I've spent around 1400-1600+ hours playing Diablo 3 since release (2012).

Drop chance is the same for season/non-season now, and both season/non-season have the same set of items available. Legendaries drop fairly frequently now even during levelling from 1-70. Plus you can upgrade yellow items->legendary using Kanai's cube (like horadric cube in d1/d2).

Season just has separate leaderboards & the season set/additional stash tab/cosmetics (portrait,wings) which you get for completing specific achievements with your seasonal character.

The combination of retroactive DPS buff on gear, and a nerf of monster HP on G/rifts is yuuge! I started two days ago and was at GR~20 within a few hours. Haven't tried my toons from previous seasons/non-seasonal yet.